In general, a driving device for an ultrasonic motor including a driving-wave-generating portion is known. For example, Japanese Patent Laying-Open No. 2008-301563 discloses this type of driving device for an ultrasonic motor.
The driving device for the ultrasonic motor in Japanese Patent Laying-Open No. 2008-301563 is constructed to apply rectangular waves (voltages) that are generated by a rectangular-wave-generating circuit (driving-wave-generating portion) to the ultrasonic motor through a low pass filter, an amplifier, and the like. In addition, the rectangular-wave-generating circuit is constructed to generate rectangular waves with a desired period in response to the instructions from a control portion. In addition, it is considered that the period of the rectangular wave generated by the rectangular-wave-generating circuit is adjusted based on the time period of one clock of a clock in the control portion as a time period unit.